The double-decked MV Asha Jaoa heading for coastal destinations and the triple-decker MV Sattar Khan bound for Dhaka were packed with people returning to work, along with their families, after a three-day holiday for the Eid-ul-Azha.

The accident occurred at about 2:00am in Hijla upazila, 282 kilometres south of the capital, as the vessels were sailing between Dhaka and Barisal in predawn dense fog.

Some survivors put the number of missing at about 150. Both launches were damaged, with the MV Asha Jaoa badly caved in, suffering most of the casualties, police said.

Police said each vessel was carrying about 500 people and both remained afloat after the collision. Prime Minister Khaleda Zia and Leader of the Opposition Sheikh Hasina expressed their condolences for the bereaved.

"We are getting conflicting reports from the scene," a river traffic official in Dhaka told Reuters.

Abdul Jabbar Biswas, an assistant to the Hijla upazila nirbahi officer (UNO), put the death count at 12 and said three children and two women were among the dead.

Survivors said they saw at least 30 bodies pulled from the water or wreckage, Associated Press reports.

A police officer earlier said: "We have rescued nearly 80 injured people, but many could be dead or alive still trapped inside the vessels."

One of the survivors, Hanufa Begum, said she lost her husband and four other family members in the crash. Hanufa was being treated in a hospital for leg injuries.

"Every one was screaming for help. There was chaos all around as many jumped overboard in panic," said Hanufa from her hospital bed.

Rescuers were rushing to the scene.

They said many passengers could have swum to safety, as the river channel was not very wide at the scene of the accident.

"Many were asleep but suddenly woke up hearing a big bang. I rushed to one side of the deck and found a bigger vessel tucked into ours. Amid cries for help I frantically looked for my sister and her family," survivor Alauddin Rari, 40, said.

Rari said his sister's husband and her three children died in the collision.

"I survived miraculously but my sister was seriously injured," said Rari attending his sister at Barisal Medical College Hospital.

"She was moved to the hospital quickly but fell unconscious after hearing her husband and children had been lost."

"Visibility was poor with thick fog covering everything at the time of the accident," Rari said.

Our Patuakhali correspondent adds: Wary relatives crowded the UNO office in Galachipa and Bangladesh Inland Water Transport Authority office in Patuakhali for information about their loved ones, feared dead or missing.

Mezbah Uddin, the Galachipa UNO, formed a two-member committee to take steps on behalf of the upazila administration and opened a control room.

Launch accidents occur often in Bangladesh and industry experts say only about 8,000 of the 20,000 launches that ply the country's extensive waterways are registered. Just 800 had fitness certificates by last July.

In one of the worst recent disasters, about 400 people drowned last July when a whirlpool swallowed the MV Nasreen, a triple-decker ferry, at a confluence of rivers near Chandpur. About 600 people were on the ferry, which had been licensed to carry

just 300.